It is superb score for a 11-year-old. Congrats!
My older daughter took SAT at age 12. She was a little short too the first time. Then she did it again a few months later and passed the 700 threshold for SET.
SET itself is more a bragging right than anything else. The free Imagine magazine is the only concrete 'benefit' from the program. The magazine is highly recommended but anyone can subscribe. Occasionally you get e-mail about some research/internship opportunities. DDs were not very interested.
You can probably put SET in the college application. But I am not sure whether it helps or not.
